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Full text of "Treatise On Applied Analytical Chemistry(Vol-1)"

SODIUM CARBONATE                                   97

Gay-Lussac degree = i-oi English, degree = 1-71 German degree = 1-58 Des-
croizilles degree.

17. Complete Analysis.100 grams of the soda are dissolved in a
beaker in hot water and the liquid allowed to stand in the hot for half an
hour, after which it is filtered through a filter dried at 100 and tared, the
insoluble matter being washed with hot water and used for determination
(a). The filtrate is collected in a litre flask and made up to the mark on
cooling, being used for the determinations (b) to (h).

(a)  INSOLUBLE   RESIDUE.   The  insoluble   matter,   dried  at   100,   is
weighed.    It is then moistened with water, lixiviated with hot, dilute hydro-
chloric acid (which dissolves the ferric oxide, alumina, calcium and mag-
nesium carbonates), washed with water, redried at 100 and weighed ;
this represents sand  and carbon (%).   After ignition the sand is weighed
alone and the carbon then obtained by difference.

(b)  TOTAL ALKALINITY AND SODIUM CARBONATE.   10 c.c. of the solution
( = i gram of substance), diluted with water, are titrated in the cold with
N-HC1  (methyl orange).    This gives total alkalinity,  due to carbonate,
hydroxide and sulphide ;  deduction from the volume of acid used of those
corresponding to the hydroxide and sulphide  (determinations c and d)
and multiplication of the remainder by 53 gives the grams of Na 2C03 per
100 grams of the soda.

(c)  SODIUM HYDROXIDE.    100  c.c. of solution  (=10 grams of   sub-
stance) are shaken in a 200 c.c. flask with excess of barium chloride (10 c.c.
of 10% solution usually suffice), made up to volume, again shaken and
left to stand ; loo c.c. of the clear liquid (not filtered) are pipetted off and
titrated with N-hydro chloric acid in presence of phenolphthalein.    This
gives alkalinity due to hydroxide and sulphide together;   subtraction of
the corresponding number of c.c. from determination (d) and multiplication
of the remainder by 0-8 gives percentage of NaOH.

(d)  SODIUM SULPHIDE.   50 c.c. of solution (=5 grams of substance)
are heated to boiling, treated with ammonia and ammoniacal silver nitrate
solution (13-82 grams Ag per litre) l run in from a burette until no further
black precipitate is produced.    To determine the end-point the more readily,
the liquid is filtered towards the end of the titration and the latter con-
tinued in the filtrate.    The number of c.c. of silver solution, multiplied
by o-i, gives the percentage of NaaS in the sample.    I c.c. of silver solution
 0-13 c.c. of N-acid (for calculations indicated in b and c).

(e)  SODIUM SULPHITE.   50 c.c. of the solution (= 5 grams of substance)
are acidified with acetic acid and titrated with N/io-iodine in presence of
starch paste.    The number of c.c. used, multiplied by 0-1261, gives the
percentage of NaoSO;) in the sample.

When sulphides are present, the number of c.c. of iodine solution used
must be diminished by that corresponding with the sulphide found as in
(d), knowing that I c.c. of silver solution = 1-3 c.c. N/io-iodine.

(/) SODIUM CHLORIDE.   With ammonia  soda, 20 c.c. (=2 grams of

1 13-82 grams of pure silver are dissolved in nitric acid, 250 c.c. of ammonia being
added and the liquid diluted to i litre,    i c.c. of this solution = 0-005 gram Na2S.
A.C.                                                                                                        7n aly for delicate colours, should not contain iron.                                                                       l.2o